Group Kolukisaoglu - Research interest
Research Interests
The research of our group focuses on the physiology and functions of chloroplasts. In this regard we have three major fields of interest.
1. D-Amino Acids in Plants
L-amino acids are primary metabolites and building blocks of proteins, and therefore matter of intensive research as essential molecules for all living organisms. However, the D-enantiomers are also regularly found throughout the complete kingdom of life (e.g. as elements of the bacterial cell wall, as parts of toxins, or as co-agonists of neurotransmitters). Nevertheless, knowledge about them in plants is rather scarce, although there is growing evidence that D-amino acids (D-AAs) fulfil different physiological functions also in plants (Fig. 1).
We started to study the metabolism of D-AAs in plants, when we found that plants react differentially to D-AA application. Plants are able to actively take up D-AAs, release them to their rhizosphere, and to degrade them enzymatically. In the course of these studies, we identified and characterized a central enzyme of D-amino acid metabolism in Arabidopsis, the plastidic D-AA transaminase AtDAT1. This enzyme turned out to be responsible for the phenomenon of “D-AA stimulated ethylene production”, which we are currently investigating in more detail.
D-AAs also play a role in the biogenesis of chloroplasts. According to the endosymbiotic theory, plastids evolved from bacterial ancestors with cell walls consisting of peptidoglycan with D-Ala and D-Glu. As previously shown in mosses, we found strong indications that chloroplast envelopes of higher plants also contain elements such as peptidoglycan (Fig. 2). In future, we will investigate biosynthesis of peptidoglycan in plants and the physiological functions of its incorporation into the plastidic envelope.
2. Functions of the PII Protein in Plants
The PII protein is a signaling protein that has been conserved throughout evolution from bacteria to higher plants. In bacteria, it interacts with a number of other proteins, thereby regulating different metabolic processes. It was assumed that the PII protein in plants is acts in a similar manner, but substantial evidence was missing.
To fill this knowledge gap, we performed interaction studies of Arabidopsis AtPII with putative interactors in planta. In these studies, the PII protein and its interaction partners were observed in characteristic aggregations in chloroplasts, which we coined as “PII foci” (Fig. 3). The formation of these PII foci was shown to be mediated by the C-terminus of PII. Furthermore, our studies revealed a novel role for plant PII proteins in the regulation of plastidic protein degradation.
3. The Herbicidal Effect of 7dSh in Plants
Recently, a C7-deoxysugar, 7-deoxy-sedoheptulose (7dSh), was isolated Synechococcus elongatus by the group of Karl Forchhammer (IMIT, University of Tübingen) as an antimetabolite. During this study, they also found that 7dSh has herbicidal activity, which makes it a promising candidate as glyphosate alternative of natural origin.
In collaboration with colleagues from Tübingen and Bielefeld, we started to evaluate the herbicidal potential of 7dSh. Therefore, we are testing this compound on a variety of plants using different formulations to develop an applicable 7dSh solution. Furthermore, we attempt to identify the molecular targets of 7dSh in plants to improve the effectiveness and applicability of this novel herbicide.